1. Field of the Invention
The subject matter disclosed generally relates to a detector that can detect trace molecules.
2. Background Information
There are detectors that are capable of detecting a trace molecule from a sample. The sample may be a gas or liquid sample taken from a room or a fluid source, respectively. It may be desirable to detect certain trace molecules to determine whether the sample contains contaminants, drugs, explosives, etc.
The detector may include an ionization stage and a mass detector stage. The ionization stage ionizes molecules within the sample and then projects the ionized molecules through the mass detector. The mass detector may be a time of flight device that determines mass based on the time at which the molecules strike a detector plate. The ionization chamber may include a light source that ionizes the sample through a photoionization process.
The sample is introduced into the ionization chamber through a single inlet port. To obtain accurate readings it is desirable to calibrate the detector before each sample is run through the device. The detector is calibrated by introducing a standard sample that may contain the molecules under investigation. Obtaining accurate readings therefore requires sequentially loading a standard sample, calibrating the detector and then introducing a test sample into the ionization chamber. This sequence can be time consuming particularly when large batches of samples are to be tested. Additionally, there may be some degradation in the detector between the time the detector is calibrated and when the test sample is actually loaded into the chamber. It would be desirable to decrease the run time and increase the accuracy of a detector.
Liquid test samples typically include water or drug samples stored in organic solvents. It is desirable to vaporize the solvent before the sample is ionized. One way to vaporize the solvent is to break the sample into aerosol droplets with a nebulizer. A nebulizer includes a co-flow of inert gas that breaks the liquid sample into an aerosol. The detector may contain a heating element that vaporizes the solvent within the aerosol.
Most nebulizers operate at atmospheric pressure because higher pressure causes more molecular collisions and assist in the vaporization process. It is sometimes desirable to operate the ionization chamber at low pressure, particularly for photoionizers. It would be desirable to provide an inlet port for liquid samples that can introduce the sample to a low pressure ionization chamber.